This invention relates generally to a method of improving fluorescence yield and, more specifically, to a method of causing a fluorescent substance-containing solution to fluoresce with an improved fluorescence yield.
It is well known that certain compounds having one or more double bonds such as aromatic hydrocarbons, dyes and vitamins can produce fluorescence by irrradiation of light. Also, certain compounds such as amino acids, sugars and metal compounds which do not fluoresce by themselves upon irradiation of light can also produce fluorescence when reacted with a fluorescence indicator. The term "fluorescence" used herein is intended to refer to emission of radiation from a substance as a result of excitation from a light source.
Fluorescence has been utilized in various fields such as for quantitative or qualitative analysis or measurement of chemical substances, laser oscillation, photochemical sensitization, and analysis of fluorescence characteristics (e.g. measurement of fluorescence life and flush photolysis). One problem associated with fluorescence is quenching, i.e. reduction of intensity of emission or reduction of quantum yield. The quenching causes reduction of sensitivity of fluorescence analysis, reduction of fluorescnce life, reduction of efficiency of energy transfer from a fluorescent substance (sensitizer) to a reaction substrate in photochemical sensitization and reduction of efficiency for obtaining outlet in laser oscillation. Such quenching has been considered to be attributed to the presence of trace oxygen in the fluorescent substance-containing solution. Thus, to cope with this quenching problem, fluorescent substance-containing solution has been subjected to an oxygen-removing treatment by purging with nitrogen or argon gas, by warming with ultrasonic wave irradiation under reduced atmosphere or by repeated freezing, evacuation and melting operations. Such methods, however, incur relatively high treatment costs and long treatment time and, thus, are not fully satisfactory.